JPS62254957A - Apparatus for casting thin aluminum alloy parts having largedimension - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for casting thin, large-sized aluminum alloy parts.

Currently, a certain number of components, such as the front panel or the engine support, are made from mechanically welded steel sheets.

In an effort to reduce the weight of components, those skilled in the art have begun to look to materials other than steel in the manufacture of parts, and in particular to aluminum alloys.

Since the parts in question are generally not flat, have cross-sections of varying thickness, and/or have protruding or raised parts such as raised edges, ribs or fins, their shaping operations may involve rolling, stamping, molding, etc. Emphasis is placed on the economics of the casting process rather than on procedures consisting of mechanical deformation such as pressing.

However, the part in question is large in size and thin (2-3II
ll) This type of component presents problems in terms of material supply, especially when the casting operation is carried out using metal molds or sand molds fed by gravity with the liquid metal. associated with filling the mold more or less completely.

In fact, methods have already been proposed to solve this problem. For example, French Patent No. 1178083 discloses as follows. [Using a mold formed by a sintered porous material with an internal relative vacuum or placed in an enclosure containing a suction passage through which the liquid metal flows under the action of gravity. The atmospheric pressure allows the metal to fit perfectly into the internal shape of the mold, and the air that previously filled this mold is evacuated through the pores of the mold. Therefore,
Parts that perfectly reproduce the shape of the mold cavity can be produced without difficulty. However, the use of molds whose entire shell is made of sintered porous material presents great difficulties, especially when casting large-sized parts, regardless of the nature of the porous material used. accompanied by.

In fact, if the material used is sintered metal, the mold must be machined prior to use in order to achieve a suitable level of dimensional accuracy for the manufactured parts, resulting in pores being blocked and air-sucking effects. decreases. In addition, these sintered metals tend to deform under heating conditions, so this type of machining in most cases does not allow accuracy problems to be completely overcome.

If the mold is made of porous ceramic material, a problem arises in that this type of material has a low resistance to thermal shock.

For the reasons mentioned above, the present applicant aims to overcome these drawbacks by providing the above-mentioned method for casting in a metal mold fixed to an enclosure fed by gravity and having a vacuum inside. A casting apparatus characterized in that the mold is formed of a material used for casting under atmospheric pressure, and further has a hole in the mold over at least one part of its thickness, into which a plug of porous material is engaged. invented.

The present invention therefore uses the method of casting in a mold mold under reduced pressure, as disclosed in French Patent No. 1 178 083, but is distinguished from the prior art by two main features:

- On the one hand, the mold is not a porous material, but is made of conventional materials used in chill mold casting processes, where there is no enclosure and the mold works under atmospheric pressure. A material of this type may be, for example, cast iron containing pearlite lamellae, which is less expensive than virtually any porous material in the pond, and also has excellent thermal shock resistance and, furthermore, excellent dimensional safety in heated conditions.

On the other hand, a hole is drilled inside the mold, i.e. on the side that comes into contact with the metal to be cast, the length of the hole being equal to the thickness of the mold, or preferably less than this thickness. A plug of porous material, which may be metal or ceramic, is fitted into the hole.

Preferably, a sintered stainless steel plug is used.

The plug transmits the reduced pressure within the enclosure to very small areas inside the mold.

If the plug does not occupy the total thickness of the mold, it can also transmit the reduced pressure through the hole in which it is fitted or to an enclosure provided behind the porous plug and under reduced pressure. It connects to the enclosure through an orifice that can be used. This structure makes it possible to reduce the amount of porous material.

The plug preferably has a diameter of less than 20 mm, so that the contact surface with the cast metal is of a very small area and the machining problems that arise with fully porous molds are avoided.

The holes are preferably located at the most remote location, avoiding the material feed point where air evacuation would take place in the worst case scenario. The number of holes required to achieve the best results will, of course, depend on the dimensions of the mold. However, it has been found to be perfectly adequate for the surface area of the holes to be equal to at most 50% of the surface area of the cast part.

As for the vacuum, it depends on the dimensions of the mold, the shape of the part, and the number and placement of plugs. The range of values used is therefore very wide (between , 1,105 Pa and 1.10'Pa.

The enclosure may completely surround the mold, or it may form two separate sections, each associated with one of the half-shell sections of the mold. Therefore, reduced pressure can be established on either or both of the two sides of the cast part as desired.

The vacuum is normally created when the metal is fed into the mold, but it is advantageous if the vacuum is offset from this time, preferably a little after this time.

The circuit for device pressure reduction may be controlled in accordance with the material feed to the mold using monitoring or regulating devices known in other applications.

The invention will now be described in more detail with reference to the accompanying drawings, which show a casting apparatus and a pressure reduction circuit in vertical cross section.

The main drawing shows a mold 1 consisting of a conventional lower mold part 2 and an upper mold part 3 with porous passages 4 extending in the illustrated embodiment according to the invention through the total thickness of the mold.

The mold parts 2 and 3 are partially separated from each other by a gap 5 or a cavity whose shape corresponds to the shape of the part to be cast. The mold cavity is associated with a liquid metal supply system consisting of a casting vessel 6. There is a stopper 7 at the bottom of this container.
An orifice is opened which can be closed off by a conduit system 8 which extends further through the upper mold part to the position of the mold cavity and is fitted with a probe 9 for detecting metal passing therethrough. Stretch it.

The figure further shows, in the downstream direction, a vacuum pump 10, a large tank 11 with a control manometer 12, a manual valve 13, an electrically actuated valve 14, a controllable timer switch coupled to the probe 9. 15, and a conduit system 1 leading to an enclosure 17 which covers only the top of the upper mold part in the example shown.
A reduced pressure generation circuit consisting of 6 is also shown.

In operation, the two parts of the mold are fitted together and the enclosure 17 is coupled to a vacuum generating circuit in which valve 13 is opened and electrically operated valve 14 is closed. The required pressure reduction value is displayed on the manometer 12, and the pointer of the timer switch 15 at the 0th order when the pump 10 is started is set at the time when the probe 9 detects the arrival of metal, the enclosure 17 and the mold cavity in correlation with this. 5 is set to the time that must elapse between when the pressure is reduced.

Next, metal is poured into the container 6 and the stopper 7 is closed. The arrival of metal in conduit 8 is detected by probe 9 and a signal is transmitted to timer switch 15 . Once the time indicated on timer switch 15 has elapsed, electrically actuated valve 14 opens and the air contained in enclosure 17, conduit 8 and mold cavity 5 is evacuated via conduit system 16 where the metal gradually fills the smallest depression in the mold cavity.

Timer switch 15 may optionally include a second pointer that controls the shutoff of electrically operated valve 14 after the reduced pressure has been applied for a desired period of time.

After the part has solidified, the mold is opened, the part is removed,
The equipment is now ready for a new casting operation.

Although the above-described device can be applied to horizontally cast parts, it is clear that it can also be applied to vertically cast parts.

The invention can be explained using the following example of use.

"Engine support stand" type, total length and width 195mm x 154m
A part made of an aluminum alloy of the ASIOG type with ribs of 10 to 35 mm in height was cast in a mold consisting of two chill-cast steel sections. The upper part has a diameter of 10
20 mm holes were drilled. A vacuum of approximately 5.104 Pascals was applied 0.12 seconds after the feed was started.

The result was a part that faithfully reproduced the shape of the mold cavity and had no internal or surface defects.

[Brief explanation of drawings]

The figure is a vertical sectional view of the casting apparatus and the decompression circuit of the present invention. 1...mold, 2...lower mold, 3...
...Upper mold, 4... Porous passage, 5...
Gap, 6... Container, F... Stopper, 8... Conduit, 9... Probe, 10...
...Vacuum pump, 11...Tank, 17.
·····enclosure.

Claims (7)

[Claims] (1) Apparatus for casting thin, large-sized aluminum alloy parts that includes a gravity-fed mold fixed to an enclosure whose interior is under reduced pressure; Apparatus formed of a material used in casting under atmospheric pressure and further provided with a hole within the mold over at least part of its thickness in which a plug of porous material is engaged. (2) The device of claim 1, wherein the porous material is sintered stainless steel. (3) The device according to claim 1, wherein each hole has a diameter of 20 mm or less. (4) The device according to claim 1, wherein the hole is located at a location remote from the mold supply location. (5) The device according to claim 1, wherein the area of the hole corresponds to at most 50% of the surface area of the cast part. (6) The apparatus of claim 1, wherein a relative vacuum is created even early when the mold is fed with metal. (7) Depressurization is achieved by means of a pump, with a tank of large dimensions equipped with a manometer to control the operation of the pump, a pipe means with a valve, and an opening regulated by a timer switch, the operation of which is applied to the metal in the mold. 2. A device as claimed in claim 1, produced through an electrically actuated valve coupled to a signal emitted by a probe that detects the moment in time when the probe is supplied.